I am sorry to learn of this situation.
Your friend's lawyer is the one you need to continue trying to contact (not the judge).
You can send your friend's lawyer an email letting them know that you are willing to submit a declaration (a written statement), or that you are willing to provide testimony on Friday morning regarding the circumstances of your friend's failure to appear.
Make sure that you are present in court - well in advance of the 8:30 a.m. appearance date (but understand that court calendars do not necessarily mean that your friend's case will be called at 8:30, so you may be there a while).
Your willingness to accept the responsibility for your friend's failure to appear is very kind, and while I highly doubt that the court is going to impose a 5 year sentence on your friend over this matter (your friend wasn't running or avoiding the court), the judge is very likely going to tell your friend that the responsibility for appearing was his, and part of his conviction, etc. is taking responsibility for his actions (not my take on this at all, but I am trying to prepare you for what I have seen a lot of judges do from their soapbox).
While I can never promise an outcome:
At the end of the day, I suspect your friend is going to get their 90 day sentence as agreed, but probably will have to undergo a very unhappy couple of minutes before the judge.